1. Field of the Invention
The present invention relates to a film slitter, film and film slitting method. More particularly, the present invention relates to a film slitter, film and film slitting method in which sectional outlines of the film formed by shearing for slitting can be neatly formed and can be free from unwanted abrasion or the like.
2. Description Related to the Prior Art
Continuous photosensitive material such as motion picture film is produced by slitting from the web or continuous sheet with a great width. The web is initially supplied in a roll form with its emulsion layer directed outwards, and is unwound at a regular speed and passed between upper and lower rotary blades. In FIG. 8, a multi-head film slitter has an upper rotary blade 2 of a circular form, which includes a plurality of blade elements arranged regularly in compliance with the number of the strips and the total width. In combination with this, a lower rotary blade 3 of a circular form is disposed and includes plural blade elements. Web 5 or continuous sheet is supported by the lower rotary blade 3 in a slitting area. To this end, the lower rotary blade 3 has a multi-drum form of rotary dies with sufficient areas for support.
When the web 5 is run in the arrow direction in the drawing, an upper blade shaft 2a supporting the upper rotary blade 2 rotates together with a lower blade shaft 3a supporting the lower rotary blade 3 at the same time. A surface of the upper rotary blade 2 directed in a forward direction and a surface of the lower rotary blade 3 directed in a backward direction are kept in contact with one another by positioning the upper and lower blade shafts 2a and 3a for contact in an overlap region of the upper and lower rotary blades 2 and 3 predetermined with reference to a running direction of the web 5. Various support mechanisms for the upper rotary blade 2 are known. U.S. Pat. No. 5,873,293 (corresponding to JP-A 7-088796) discloses a structure for biasing the upper rotary blade 2 in the axial direction of the upper blade shaft 2a to maintain its contact with the lower rotary blade 3.
The upper and lower rotary blades 2 and 3 are supported vertically to an axial direction of the upper and lower blade shafts 2a and 3a. The upper and lower blade shafts 2a and 3a are disposed to extend perpendicularly to the running direction of the web 5. The web 5 is slitted by shearing while passed between the upper and lower rotary blades 2 and 3, so that continuous photo films 6 as elongate strips are formed at a regular width. A winding reel winds each of the continuous photo films 6. Note that selvedge portions 7 are formed from the web 5 beside the continuous photo film 6, and are discarded.
In FIGS. 9A, 9B and 9C, states of slitting are illustrated. Beveled surfaces 2b and 3b of a cutting edge are formed with respectively the upper and lower rotary blades 2 and 3. When the web 5 comes in the slitting area between the upper and lower rotary blades 2 and 3, the upper rotary blade 2 moves down in a direction from an emulsion layer 8 toward a film support 9. After the continuous photo film 6 is slitted by the upper rotary blade 2 as depicted in FIG. 9C, vertical surfaces of the upper and lower rotary blades 2 and 3 contact one another.
In FIGS. 10A and 10B, the continuous photo film 6 obtained by slitting is illustrated as viewed in a section taken on a line perpendicular to the running direction of the continuous photo film 6. In FIG. 10A, a shape obtained by slitting of the upper rotary blade 2 is depicted. In FIG. 10B, a shape obtained by slitting of the lower rotary blade 3 is depicted. In FIG. 10A, a sectional outline 6a is defined on a first one of two lateral edges of the continuous photo film 6. In FIG. 10B, a sectional outline 6b is defined on a second one of the lateral edges. Each one of the continuous photo film 6 obtained by slitting comes to have the sectional outlines 6a and 6b. On the sectional outline 6a on the upper blade side, an edge portion of the film support 9 protrudes from an edge portion of the emulsion layer 8 in a lower portion as viewed in the thickness direction. On the sectional outline 6b on the lower blade side, an edge portion of the film support 9 protrudes from an edge portion of the emulsion layer 8 at the center as viewed in the thickness direction.
In short, the sectional outlines along the lateral edges of the continuous photo film 6 are in the different shapes as a product slitted in the known film slitter. There arises a problem in the continuous photo film 6 of which an edge burr of the film support 9 occurs and protrudes laterally in an example of continuous film such as motion picture film. The edge burr of the film support 9 is likely to rub a flange of an winding reel or idler wheel for use in the movie projection for a long time. Fine dust or particles will be created and scattered in the course of abrasion.
Examples of motion picture films of 35 mm width include a camera film, duplicating film (intermediate film) and print film. At first, images are photographed on the camera film as original film. The duplicating film is used for duplication by use of the camera film. Then the print film is used to produce prints for the purpose of movie projection. Printers of specified purposes are used for printing of any of motion picture films. In FIGS. 11A and 11B, examples of device for printing operation are illustrated, including a winding reel 10 with a flange 10a, and an idler wheel 11 or idler reel with a flange 11a. In FIG. 11A, it is likely that the continuous photo film 6 is wound about the winding reel 10 with skew to the flange 10a. In FIG. 11B, a transport direction of the continuous photo film 6 slightly changes so that an edge of the continuous photo film 6 is rubbed by the flange 11a. 
The duplicating film and the print film having the emulsion layer are wound in the roll form. There are predetermined directions of the duplicating film and the print film for operation of duplication and printing in the art of the motion picture film, the directions including a running direction, winding direction, and opposing direction between the films. In a structure to transport the continuous photo film 6 in a printer, an end face of a first lateral edge of the continuous photo film 6 supported by the lower rotary blade 3 comes to contact the flange 10a or 11a without contact of a second lateral edge of the continuous photo film 6 formed by slitting with the upper rotary blade 2. In FIG. 10B, the sectional outline 6b on the side supported by the lower rotary blade 3 has an edge burr as a portion of the film support 9 of PET protruding remarkably in a projecting position B at the center. Fine dust or particles are likely to occur in frictional contact with the flange 10a or 11a, to break a mechanism for transporting the continuous photo film 6, or to contaminate the continuous photo film 6.